[PATCH] arm: KVM: Fix idmap overlap detection when the kernel is idmap'ed

[Marc Zyngier]

We're trying hard to detect when the HYP idmap overlaps with the
HYP va, as it makes the teardown of a cpu dangerous. But there is
one case where an overlap is completely safe, which is when the
whole of the kernel is idmap'ed, which is likely to happen on 32bit
when RAM is at 0x8000000 and we're using a 2G/2G VA split.

In that case, we can proceed safely.

Reported-by: Christoffer Dall <christoffer.dall at linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>
---
 arch/arm/kvm/mmu.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index bda27b6..4e165ff 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -1714,7 +1714,8 @@ int kvm_mmu_init(void)
 		 kern_hyp_va(PAGE_OFFSET), kern_hyp_va(~0UL));
 
 	if (hyp_idmap_start >= kern_hyp_va(PAGE_OFFSET) &&
-	    hyp_idmap_start <  kern_hyp_va(~0UL)) {
+	    hyp_idmap_start <  kern_hyp_va(~0UL) &&
+	    hyp_idmap_start != __hyp_idmap_text_start) {
 		/*
 		 * The idmap page is intersecting with the VA space,
 		 * it is not safe to continue further.
-- 
2.1.4